f3a5bfb1b9
This PR adds validations for the new new funnel/serve commands under the following rules: 1. There is always a single config for one port (bg or fg). 2. Foreground configs under the same port cannot co-exists (for now). 3. Background configs can change as long as the serve type is the same. Updates #8489 Signed-off-by: Marwan Sulaiman <marwan@tailscale.com>